1. Field of the Invention
The present invention pertains to an aircraft step module adapted for attachment to the exterior of an aircraft fuselage and including a retractable step member mounted on a linkage which provides for biasing the step in the retracted position.
2. Background Art
The design of many types of aircraft fuselages and cabin structures is such that there is no provision for passenger or cargo loading steps or surfaces extending from the cabin doorway. This is necessary because of the space requirements of structural components of the fuselage. Moreover, there are increasing numbers of auxiliary loading and unloading structures provided at many airports and related facilities. However, it is often desirable to provide for the addition of aircraft loading and unloading steps or platforms which make boarding and exiting the aircraft easier and safer due to the height of the cabin floor from the ground surface when the aircraft is parked away from ground based boarding facilities.
It is also often desirable to be able to retrofit access steps to aircraft which are designed for utility purposes but which often are converted for primarily passenger service. For example, a number of state of the art helicopter designs are intended primarily for utility purposes. Their fuselage structures are not designed primarily for passenger carrying and accordingly, no provisions are made at the loading doors for boarding steps or the like. However, the increased use of helicopters for business and personal travel has resulted in the adaptation of a number of helicopter designs for passenger service. In this respect it has become desirable to provide auxiliary devices such as boarding steps or the like to permit easy boarding and unloading of passengers.
In this regard, it has become particularly desirable to provide a modular unit which may be added to the exterior of the aircraft fuselage and thereby not requiring major structural modifications which are expensive and, of course, cannot compromise the integrity of the fuselage structure. However, the addition of appendages to the exterior of an aircraft structure must be done in such a way as to be compact and lightweight as possible and be configured to minimize aerodynamic drag. At the same time, however, structures which are adapted to support the weight of persons boarding or disembarking from the aircraft must possess adequate strength to support the loads incurred by such use. It is also important that structures which are deployed from a retracted position forming a streamlined body to a working position, be provided with means to minimize the chance of accidental deployment to the working position while the aircraft is in flight. Such action can, of course, seriously affect the handling characteristics of aircraft due to unbalanced aerodynamic forces.
All of the abovementioned desiderata and requirements for aircraft structures are difficult to meet in a structure which is economical to manufacture. However, in accordance with the present invention, substantially all of the objectives discussed hereinabove have been met in an improved modular aircraft step device which is retractable from a working or deployed position to a position which minimizes the effect of aerodynamic forces on the aircraft.